1. Technical Field
The invention relates to capacitive sensors, and, more particularly, to capacitive sensors that measure a bend angle.
2. Description of the Prior Art
Interfaces that sense the position and orientation of the user's fingers, hands, head or other body joints are an integral part of many applications, such as computer game systems, virtual keyboards, interactive visualization, and three-dimensional graphics systems.
In existing systems, three-dimensional position sensors, such as those manufactured by Polhemus Corp., are typically affixed to the user's body parts (i.e. hands and head) to determine the position of the user's respective body parts. In addition, the user typically wears gloves that include bend angle sensors that measure the bend angle of the user's fingers. Bend angle sensors developed to date have either been inexpensive yet inaccurate, or accurate and very expensive.
For example, Mattel manufactures an inexpensive hand-position-interface glove that uses a flexible resistor whose resistance changes with bending. This technique has limited bend angle sensitivity and reproducibility. In another example, VPL Research Inc. has developed an expensive hand position interface glove that measures finger bend angle by sensing the loss of light from bent optical fibers. This sensing technique gives no information about the direction of the bend, only its magnitude.
Thus, there is a need in the art to provide an accurate yet inexpensive means of sensing the bend angle of fingers and other body parts. More particularly, there is a need to provide a sensor for measuring "backwards" bending (for example, the bending of the wrists "up and down"), and for measuring perpendicular planes of bending (for example, a first plane characterized by the "up" and "down" bending of the thumb or wrist and a second plane characterized by the "sideways" bending of the thumb or wrist).